The present invention applies to improvements to caulking guns and, more specifically, to an adjustable piston packing expander for expanding the packing within the piston assembly of the caulking gun.
Industrial quality caulking guns, such as that shown generally at 10 in FIG. 1 of the drawings, utilize a steel barrel 11 into which there is fitted a piston assembly carried by a piston rod 12. The piston assembly, which includes at least one packing, serves to extrude caulking compound through the barrel as the piston rod advances to ultimately extrude the caulking compound through the gun nozzle 13 carried by the front cap 14 generally threaded onto the end of the barrel 11. The piston rod 12 is advanced by means of a hand actuator 15 operating through a well known drive mechanism in the rear of the gun.
Industrial quality guns such as that shown in FIG. 1 of the drawings are filled generally in two different manners. The first is by unscrewing the front cap 14 and engaging the front of the barrel with a bulk container of caulking compound whereupon the piston assembly is retracted rearwardly to draw in a charge of caulking compound from the bulk container. A second and more recently available method of filling the barrel with caulking compound is by the use of what are known as "sausage" packages 16 as shown in FIG. 2. These "sausage" packages are tubelike members formed generally of a thin plastic material such as mylar which is generally in the range of 2 mils thickness. Such packages are filled and are approximately the length of the barrel 11 and are clamped on or tied off at their ends by an appropriate clamp or tie 17.
In use the "sausage" package is inserted into the barrel after the piston is retracted. Thereafter, the end of the package closest the front cap 14 is cut open and the front cap threaded back onto the barrel. The operation of the gun is as in the conventional manner in that the hand actuator 15 drives the piston rod and piston assembly forward compressing and extruding the compound within the package 16 through the nozzle 13 of the gun.
A persistent problem in industrial guns of the nature above described is wear on the piston packing which will permit bypass of the piston by the caulking compound. Additionally, in those situations where the "sausage" type package is used a problem is encountered in that the very thin package, as it is collapsed by the piston assembly, will tend to override or jam between the piston packing and the cylinder walls. As this occurs, the force required to extrude the caulking compound from the gun increases. Additionally, once the caulking compound has been exhausted, difficulty is sometimes encountered in extracting the empty and thin package from the gun barrel.
A need exists in the caulking gun industry and particularly in the industrial grade caulking guns for a means by which the piston packing can be quickly and easily adjusted to accommodate for manufacturing toelrances, wear and other conditions in order to provide for the optimum pressure of the packing against the gun barrel walls. A further need exists for a caulking gun in which the piston packing pressure can be adjusted to provide for use of the gun with lower viscosity materials and which provides for cleaner scavenging and less cleanup. Maintenance of the optimum pressure will ensure ease of movement of the pistion assembly along the gun barrel walls while, at the same time, preventing caulking compound override of the packing assembly in the case of bulk compound charge in the gun barrel and, in the case of use of the "sausage" packages, prevent interference or bypass of the package and the piston packing.